Self-propelled milling machine, as well as method for controlling a self-propelled milling machine

ABSTRACT

In a self-propelled construction machine, specifically, a road milling machine, a surface miner or a recycler, for milling a ground surface, comprising a machine frame with a longitudinal axis, comprising a chassis with wheels or tracked ground-engaging units which support the machine frame, comprising a controller for the travelling and milling operation, comprising a height-adjustable working drum, comprising a slewable transport conveyor arranged in front of or behind the working drum as seen in the direction of travel of the milling machine with a discharge end from which worked-off milling material is dischargeable onto a point of impingement on a loading surface of a means of transport, wherein the transport conveyor is slewable about, as a minimum, a first slewing axis extending essentially orthogonal to the machine frame laterally under a slewing angle, wherein the controller comprises a control system which controls, as a minimum, the slewing angle of the transport conveyor automatically in the travelling and milling operation, it is specified for the following features to be achieved: that the control system, at least as a function of a virtual trajectory for positioning the transport conveyor which is freely specifiable in a stationary coordinate system that is independent of the position and alignment of the machine frame, controls, by means of open-loop control or closed-loop control, at least the slewing angle of the transport conveyor automatically in such a fashion that a reference point of the transport conveyor always remains on the specified trajectory in the case of a change in position of the machine frame within the coordinate system.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims benefit of German Patent Application No. 10 2016222 589.8, filed Nov. 16, 2016, and which is hereby incorporated byreference.

BACKGROUND

The invention relates to a self-propelled milling machine and a methodfor controlling a self-propelled milling machine in accordance withclaims as submitted herewith.

The self-propelled milling machine, specifically, road milling machine,surface miner or recycler, comprises a machine frame with a longitudinalaxis, a chassis with wheels or tracked ground-engaging units whichsupport the machine frame, as well as a controller for the travellingand milling operation and a height-adjustable working drum. A slewablelast or single transport conveyor of specified length is arranged infront of or behind the working drum as seen in the direction of travelof the milling machine, where said transport conveyor is slewableautomatically about, as a minimum, an essentially vertical first axislaterally under a slewing angle. Such milling machines are known from EP2 700 748.

The milling machine comprises a controller for the travelling andmilling operation, as well as a working drum for the milling of, forexample, a road pavement. A transport conveyor device comprising, as aminimum, one transport conveyor is located in front of or behind theworking drum as seen in the direction of travel. Depending on where thetransport conveyor is arranged, the milling machine is in the followingcalled a front-loading/rear-loading milling machine. The transportconveyor may be slewed, relative to the longitudinal axis of the millingmachine, laterally under a specifiable slewing angle to the left orright and may be adjustable in height via a specifiable elevation angle.The transport conveyor comprises a discharge end at which the millingmaterial is unloaded, due to the conveying speed and the elevationangle, onto the loading surface of a transport vehicle via a flight pathin the form of a parabolic trajectory.

A problem consists in the fact that the operator of the milling machinealso needs to control loading of the loading surface by adjusting theslewing angle, the elevation angle, where appropriate, and/or theconveying speed of the transport conveyor and, by doing so, isdistracted from the actual task of carrying out the milling operation. Acorrection of the slewing angle may be required, for example, whenaltering the direction of travel of the milling machine or of thetransport vehicle.

In case of a rear-loading milling machine, problems also arise incoordinating the milling machine with the transport vehicle especiallysince the transport vehicle needs to drive behind the milling machine inreverse travel. An even higher level of stress results for the operatorof the milling machine as he needs to control the milling process inforward travel on the one hand and needs to monitor loading of thetransport vehicle behind the milling machine as seen in the direction oftravel on the other hand, and in the process needs to control mainly theslewing angle and the elevation angle, where appropriate, and/or theconveying speed of the transport conveyor device.

The transport conveyor may be longer than the actual milling machine andusually measures approx. 5 m to approx. 8 m in length.

An automatic control of the slewing angle is specified from EP 2 700 748which enables the operator of the milling machine to concentrate on themilling operation and on driving along a specified milling track. Themilling machine can thus be moved in the direction of travel similar toa vehicle with a towed single-axle trailer.

BRIEF SUMMARY

Proceeding from such prior art, it is an object of the invention tocreate a self-propelled milling machine, as well as a method forcontrolling the milling machine in which a simplified execution of theloading process can be realized in any operating situation.

The invention advantageously specifies that a control system, at leastas a function of a virtual trajectory for positioning the transportconveyor which is freely specifiable in a stationary coordinate systemthat is independent of the position and alignment of the machine frame,controls, by means of open-loop control or closed-loop control, at leastthe slewing angle of the transport conveyor automatically in such afashion that a reference point of the transport conveyor, preferably thedischarge end of the transport conveyor or the point of impingement ofthe worked-off milling material, always remains on the specifiedtrajectory in the case of a change in position of the machine framewithin the coordinate system.

The reference point, for example, the discharge end of the transportconveyor or the point of impingement of the worked-off milling material,is guided in an advantageous manner along a trajectory that is freelyspecifiable and is determined virtually within a coordinate system thatis stationary relative to the ground surface. In this arrangement, thereference point of the transport conveyor is a virtual or real locus onthe transport conveyor or in the extended axis of the same whichrepresents the position of the transport conveyor.

With the position and alignment of the milling machine within thecoordinate system and the course of the trajectory in the coordinatesystem being known, the control system can determine the slewing angleof the transport conveyor to be currently adjusted relative to themilling machine by means of calculation in such a fashion that, forexample, the discharge end of the transport conveyor or the point ofimpingement of the worked-off milling material, respectively, alwaysremains on the specified trajectory.

To initialize the automatic open-loop control or closed-loop controlprocess, the coordinate system may be determined relative to the machineframe, for example, by determining the starting position of the machineas the origin of the coordinate system. In this arrangement, the slewingaxis of the transport conveyor relative to the machine frame may, forexample, form the reference point of the milling machine for thestarting position. The Y-alignment of the coordinate system may then,for example, extend parallel to the longitudinal axis of the machineframe. During the initialization, the trajectory determined in thecoordinate system should preferably extend through the current positionof the reference point, for example, of the discharge end or the pointof impingement, respectively.

The coordinate system or the trajectory, respectively, is alignedrelative to the milling machine during initialization only, and isstationary after the initialization and therefore independent of themachine position. After the initialization, the machine thus moves insaid determined coordinate system.

In the case of closed-loop control, the trajectory may be considered ascommand variable, the change in position of the milling machine asdisturbance variable, and the slewing angle as controlled variable.

As a result, the control system can minimize the distance between thereference point of the transport conveyor and the trajectory bycontrolling the slewing angle.

It is preferably specified for the control system to continuously detectthe current position and alignment of the machine frame in thecoordinate system and to determine the slewing angle to be adjusted as afunction of the position of the stationary trajectory relative to themachine frame or to the reference point of the transport conveyor.

A position determination is continuous also when performed in specifiedtime intervals, for example, at a frequency of 1 Hz.

In a particularly preferred embodiment, it is specified that theposition of the trajectory relative to the stationary coordinate systemis alterable in the control system, and that the control systemrecalculates the slewing angle to be adjusted in case of an alteredposition of the trajectory in the coordinate system.

This offers the advantage that the operator can determine the positionof a trajectory not only at the beginning of a milling process but canalso alter the same during the operation without having tosimultaneously give up the automatic adjustment of the slewing angle.

To this effect, the control system may comprise a control operatingelement or an input device, respectively, operable by the operator, bymeans of which a different trajectory is determinable in the coordinatesystem in the case of a desired change in the position of the currenttrajectory, or by means of which the alignment of the current trajectoryin the coordinate system is slewable about a preset virtual axis ofrotation extending essentially orthogonal to the ground surface.

The operator can therefore enter a fundamentally altered trajectory intothe control system on the one hand, or can alter the alignment of atrajectory already preset in the coordinate system.

An altered course of the trajectory may also take the form of, forexample, the existing trajectory being shifted in parallel if, forexample, the means of transport is not driving in the extended axis ofthe milling track but in parallel to the milling track.

When rotating the preset trajectory about a virtual axis of rotation,the axis of rotation may be adjustable, in the extended axis of thetransport conveyor, in a range between the discharge end of thetransport conveyor and the calculated point of impingement, with thevertical axis of rotation preferably extending through the discharge endor the calculable point of impingement.

In an advantageous embodiment, it is specified for the control system tocomprise an image-displaying device which graphically represents, as aminimum, the relative position of the currently selected trajectory inrelation to the transport conveyor and/or to the longitudinal axis ofthe machine frame and/or to the position of the loading surface of themeans of transport.

The visual representation of the trajectory enables the operator tomonitor the automatic control of the slewing angle and, should the needarise, to alter the direction and the course of the trajectory by meansof the control operating element.

To calculate the current position and alignment of the machine frame inthe coordinate system, the control system may continuously detect thesteering angle and the distance traveled, or the steering angle and thecurrent travel speed, or may continuously detect, by means of GPSsensors, the position and alignment of the machine frame relative to thecoordinate system.

In addition, different steering modes may also be taken intoconsideration in the calculation such as, for example, the coordinatedsteering of all wheels or tracked ground-engaging units by means ofsteering both axles in the same or in opposite directions or steering asingle axle only.

The control system may, for example, determine the orthogonal distance aof a reference point on the machine frame, preferably on thelongitudinal axis, to the trajectory, and the angle between thelongitudinal axis of the machine frame and the trajectory.

The transport conveyor may be inclinable about a second axis extendingorthogonal to the first slewing axis under a specified elevation angle,where the control system additionally continuously controls the slewingangle of the slewable transport conveyor automatically as a function ofat least one of the following parameters, namely, the longitudinal andtransverse inclination of the machine frame, the advance speed, theelevation angle of the transport conveyor and the conveying speed of themilling material, in such a fashion that, in any steering situationduring forward travel or reverse travel, the slewable transport conveyorassumes a specified slewing angle in which the reference point of thetransport conveyor is, essentially, guided along the trajectory.

The transport conveyor may also be inclinable about a second axisextending orthogonal to the first slewing axis under a specifiedelevation angle, where the transport conveyor discharges the millingmaterial onto the loading surface of the means of transport at aspecified conveying speed. In addition to the slewing angle of theslewable transport conveyor, the control system may control, by means ofopen-loop control or closed-loop control, the elevation angle and/or theconveying speed of the transport conveyor automatically in such afashion that the reference point of the transport conveyor alwaysremains on the specified trajectory in the case of a change in positionof the machine frame within the coordinate system.

It may additionally be specified for the control system to continuouslylocate the position of the loading surface in the coordinate system inorder to always keep the reference point of the transport conveyor, forexample, the discharge end or the point of impingement along thespecified trajectory within the loading surface.

The control system may comprise, as a minimum, one detector which, withthe steering mode being known, directly or indirectly detects thesteering angle specified by the steering controller and the distancetraveled, or the steering angle and the travel speed.

The control system may receive signals from a distance measuring deviceby means of which the distance to a means of transport is detectable.

In a preferred embodiment, it is specified for the control system tocomprise an image-capturing device which creates a real or virtual viewfrom the perspective of the operator or from the bird's eye perspective,preferably above the virtual axis of rotation of the trajectory, wherethe control system inserts the virtual trajectory into the image createdby the image-capturing device and displayed on the image-displayingdevice.

The trajectory is preferably a straight line or a curve with a specifiedcurve radius. The trajectory may finally also, for example, be a curveprogression following the course of the road which is definable as afunction of a distance traveled or within the parameters of a selectedcoordinate system.

The straight line or curve may be entered in a relative or absolutecoordinate system through, for example, a mathematical function, a curveprogression through, for example, a position data field in the form ofcoordinate data related to the coordinate system.

The invention furthermore relates to a method for controlling aself-propelled milling machine.

Further advantageous features can be inferred from the description.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Hereinafter, embodiments of the invention are illustrated in more detailwith reference to the drawings.

The following is shown:

FIG. 1 represents a rear-loading road milling machine,

FIG. 2 represents a front-loading road milling machine, and

FIG. 3 represents a schematic representation of a starting position ofthe milling machine in the coordinate system, as well as the automaticcontrol of the slewing angle in the case of a change in position of themilling machine,

FIG. 4 represents a schematic representation according to FIG. 3 with adifferent position of the trajectory,

FIG. 5a represents the slewability of the trajectory about a virtualslewing axis,

FIG. 5b represents the parallel shift of a trajectory,

FIG. 5c represents a curve-shaped trajectory,

FIG. 6 represents an example of the calculation of the slewing angle tobe adjusted, and

FIG. 7 represents a schematic circuit diagram of the control anddetection device.

DETAILED DESCRIPTION

The following description relates to self-propelled milling machines,specifically to road milling machines but also to surface miners andrecyclers.

FIG. 1 shows the example of a rear-loading milling machine 1 b in whichthe transport vehicle 10 travels behind the milling machine in reversetravel.

Provided that sufficient space is available on the side next to themilling machine 1 b, the means of transport 10, for example, a truck,may also be moved next to the milling machine 1 b in forward travel.

FIG. 2 shows a milling machine using as an example a front-loading roadmilling machine 1 a. The milling machine 1 a, 1 b comprises a machineframe 2 which is supported by a chassis 4 comprised of, for example,tracked ground-engaging units or wheels, said chassis 4 being connectedto the machine frame 2 via no less than two height adjustment devices inthe form of lifting columns 5. As can be inferred from FIG. 2, theembodiment specifies four lifting columns 5 by means of which themachine frame 2 can be brought into a specifiable plane that extendspreferably parallel to the road surface 6 which the trackedground-engaging units of the chassis 4 stand on.

The milling machine 1 a shown in FIG. 2 comprises, between the trackedground-engaging units of the chassis 4 as seen in longitudinal directionof the milling machine 1 a, a working drum 22.

The working drum 22 may be adjustable in height via the lifting columns5 supporting the machine frame 2 or relative to the machine frame 2.

The milling machines 1 a, 1 b may comprise steerable trackedground-engaging units and/or wheels.

Other designs of a milling machine 1 b may also feature the working drum22, for example, at the height of the rear tracked ground-engaging unitsor wheels of the chassis 4, as is also depicted in FIG. 1.

A transport conveyor 12 for transporting away the milled-off millingmaterial may also be arranged at the front end 7 or at the rear end 8 ofthe milling machine 1 a, 1 b.

The directions of travel of the respective vehicles are each indicatedin FIGS. 1 and 2 by arrows 48.

In the embodiment according to FIG. 2, the milling material 14 milledoff by the working drum 22 is transferred, via a first transportconveyor 11, to a second, slewable transport conveyor 12 which unloadsthe milling material 14 onto the loading surface 15 of the means oftransport 10. As a function of the conveying speed of the transportconveyor 12, the milling material 14 is not immediately unloaded at thedischarge end 13 of the transport conveyor 12, but the milling material14 rather follows a parabolic trajectory so that the point ofimpingement 16 on the loading surface 15 is located at a distance fromthe free discharge end 13 of the transport conveyor 12 in the extendedaxis of the same. The transport conveyor 12 can be slewed about aslewing angle α from a neutral position to the left or to the right viapiston-cylinder units 18 in order to be able to unload the millingmaterial 14 onto the loading surface 15 even when cornering or in theevent of the transport vehicle 10 driving in an offset track. Inaddition, the operator of the milling machine 1 a, 1 b can adjust theelevation angle of the transport conveyor 12 by means of apiston-cylinder unit 20. The elevation angle has an influence on theparabolic trajectory of the milled material 14 and on the position ofthe point of impingement 16, as has the conveying speed of the transportconveyor 12.

In this context, the point of impingement 16 signifies the point atwhich the milling material 14 discharged by the transport conveyor 12impinges on the loading surface 15 of the means of transport 10. Inaddition to the slewing angle of the transport conveyor 12, said pointof impingement 16 is also a function of the inclination and theconveying speed of the transport conveyor 12, as well as, to a lesserextent, of the height of the loading surface 15 and the filling state ofthe same. With the slewing angle α of the transport conveyor 12 beingknown, the point of impingement 16 can therefore be calculated withsufficient accuracy. For a more accurate calculation, the parameters ofelevation angle and/or conveying speed and/or properties of the means oftransport 10 may continue to also be taken into consideration.

The currently adjusted elevation angle about a horizontal axis 21, orthe slewing angle α about a vertical slewing axis 23, respectively, aswell as the current steering angle are reported to a control system 24which may furthermore comprise, as a minimum, one detector 26 whichcontinuously detects the position of the loading surface 15. Saiddetector 26 may be arranged either at the milling machine 1 a, 1 b, atthe end facing the transport conveyor 12, or at the free discharge end13 of the transport conveyor 12.

Furthermore, further detectors generally known from prior art may be inplace, which directly or indirectly detect the current slewing angle andthe elevation angle of the transport conveyor 12. A direct detection maybe effected at the slewing axis 23, an indirect detection may beeffected, for example, when the slewing/elevation angles are adjusted bymeans of piston-cylinder units 18, 20, and a path measuring systemmonitors the position of the piston-cylinder units 18, 20. Said positioncan then be assigned to a specific slewing/elevation angle.

The control system 24 may be integrated into the controller 3 for thetravelling and milling operation operated by the operator or may, as aminimum, be connected to the same in order to, where appropriate, alsoobtain data on the travel speed, the distance traveled and/or a detectedsteering angle of the milling machine 1 a, 1 b and the conveying speedof the transport conveyor 12.

The control system 24 uses a stationary coordinate system independent ofthe position and alignment of the machine frame 2 which is initializedat a start of the milling process and stored in the control system 24 ina memory 58. The control system 24 controls the slewing angle α of thetransport conveyor 12 automatically as a function of the currentposition of the milling machine 1 a, 1 b and a trajectory 25 specifiedin the coordinate system. The coordinate system is stationary vis-à-visthe ground surface 6 but may, during initialization, be determined inthe control system 24 based on the starting position of the millingmachine in that it is, for example, determined in relation to thecurrent position of the machine during initialization. For example, theposition of the machine frame 2 or of a part of the machine, forexample, the position of the slewing axis 23, respectively, may beplaced in the origin of the coordinate system. As is depicted in thedrawings, the origin may also be placed at an offset to the position ofthe slewing axis 23 or in any other position the distance of which fromthe slewing axis 23 is known. The alignment of the machine frame 2, thatis, the longitudinal axis 9 may be placed parallel to the Y-axis of theco-ordinate system.

A freely specifiable virtual trajectory 25, for example, in the form ofa straight line, as can be inferred from the embodiments according toFIGS. 3 to 5 a, may be entered in the control system 24 and integratedand stored in the stationary coordinate system. In the figures, thecontinuously drawn representation shows a starting position, whereas thedotted representation shows the situation after a change in position ofthe machine frame 2 or of the loading surface 15, respectively. By meansof the current machine position in the coordinate system and the fixedtrajectory 25 in the coordinate system, the control system 24 cancontrol, by means of open-loop control or closed-loop control, theslewing angle α of the transport conveyor 12 about the vertical slewingaxis 23 automatically in such a fashion that, in the case of a change inposition of the machine frame 2, a reference point of the transportconveyor 12 is always kept on the trajectory specified. Mostappropriately, such reference point is, for example, the discharge end13 of the transport conveyor 12.

FIG. 3 shows a simple embodiment in which the longitudinal axis 9 of themachine frame 2 of the milling machine 1 a and the longitudinal centralaxis 17 of the transport conveyor 12 are aligned rectilinearly to oneanother in the starting position, that is, the current slewing angle αof the transport conveyor 12 is zero relative to the machine frame 2.

In the extended axis of the transport conveyor 12 beyond the dischargeend 13, the point of impingement 16 on the loading surface 15 of themeans of transport 10 is shown which, in the starting position, is alsoaligned collinearly to the longitudinal central axis 17 and thelongitudinal axis 9.

In FIGS. 3 and 4, the coordinate system is aligned, with its Y-axis,parallel to the longitudinal axis 9 of the machine frame 2, with theorigin being depicted at an offset to the slewing axis 23 for bettervisualization, so that the starting position of the machine in FIG. 3has the coordinates (x, 0). It is preferred, however, to determine theorigin of the coordinate system automatically in relation to a fixedreference point of the machine frame, for example, the slewing axis 23,with the Y-axis being aligned in parallel to the longitudinal axis 9 ofthe machine frame 2. Alternatively, the Y-axis may, for example, bealigned parallel to the longitudinal axis 17 of the transport conveyor12.

Proceeding from such situation, in which the machine frame 2, thetransport conveyor 12, the means of transport 10 and the specifiedtrajectory 25 are collinear, the situation is depicted in dotted linesin FIG. 3 in which the milling machine 1 a is required to drive around amanhole cover 42. The process results in a change in the position andalignment of the machine frame 2 in the determined coordinate system. Bymeans of the continuous detection of said changes in position andalignment, the control system 24 can automatically establish andcontrol, by means of closed-loop control, the required alteration of theslewing angle α for the transport conveyor 12. It can be inferred fromthe dotted representation that despite the change in the position of themilling machine 1 a, due to this control process, the point ofimpingement 16 of the milling material always remains on the trajectory25.

It is understood that, in lieu of the point of impingement 16, adifferent reference point to the transport conveyor 12 which is afunction of the slewing movement of the transport conveyor 12 may alsobe selected such as, for example, the discharge end 13, or a differentreference point on the transport conveyor 12 or in the extended axis ofthe same.

FIG. 4 shows a starting position in which the milling machine 1 a, thetransport conveyor 12 and the means of transport 10 are initiallyaligned collinearly but the specified trajectory 25 has been altered insuch a fashion that it extends, proceeding from the starting positiondepicted, obliquely to the longitudinal axis 9 of the machine frame 2and the longitudinal central axis 17 of the transport conveyor 12. Suchintervention may be effected, for example, when the operator of themilling machine perceives that the means of transport 10 is performing asteering movement and is therefore no longer moving collinearly to thelongitudinal axis 9 of the machine frame 2 or the transport conveyor 12,respectively. Such a situation may arise, for example, when the means oftransport 10 enters a bend ahead of the milling machine 1 a, 1 b.

After both the means of transport 10 and the milling machine 1 a havechanged their positions, it is apparent that, in this case also, theslewing angle α can be controlled, by means of closed-loop control,automatically without any intervention by the operator in that, in thiscase, the point of impingement 16 follows the altered trajectory 25automatically during the forward travel of the milling machine 1 a.

FIGS. 5a, 5b, 5c show further embodiments in which the operator can varythe position of the trajectory 25 within the coordinate system.

An operating element 27 is specified for this purpose which is connectedwith the control system 24. In the case of a desired change in theposition of the current trajectory 25, an altered course of thetrajectory 25 in the coordinate system is determinable via the operatingelement 27 in that, for example, the trajectory 25 is rotated in thecoordinate system (FIG. 5a ) or shifted in parallel (FIG. 5b ). Thecontrol element 27 may, for example, comprise a rotary switch which isrotatable in two directions for the purpose of rotating the trajectory,and is movable laterally to the left or right for the purpose ofparallel shifting. Furthermore, the operating element 27 may comprise aninput device. Alternatively, an input of data may be effected via aninput device of the controller 3 not depicted.

If a different, for example, a curved trajectory 25 (FIG. 5c ) or acurve progression is to be entered, the input of data may also beeffected via the operating element 27.

In FIG. 5a , the current trajectory 25 is slewed about a preset virtualaxis of rotation 19 extending essentially orthogonal to the groundsurface 6. The vertical axis of rotation 19 may be adjustable in theextended axis of the transport conveyor 12 preferably in a range betweenthe discharge end 13 and the calculated point of impingement 16, where,however, the virtual axis of rotation 19 is to preferably extend throughthe discharge end 13 (FIGS. 1 and 6) or through the point of impingement16 (FIGS. 2 and 4). It may furthermore be specified that the position ofthe virtual axis of rotation 19 can be altered by the machine operatorvia the operating element 27.

The parallel shift of the trajectory 25 depicted in FIG. 5b may berequired, for example, at the beginning of the milling work when thesystem is prepared for loading onto a means of transport 10 drivingparallel to the milling track.

During initialization, the trajectory 25 is collinear to thelongitudinal axis 9 of the machine frame 2 and is then shifted inparallel in the coordinate system prior to the start of the millingprocess in such a fashion that it is collinear to the longitudinalcentral axis of the means of transport 10.

An image-displaying device 30 may graphically represent, as a minimum,the relative position of the currently selected trajectory 25 inrelation to the transport conveyor 12 and/or to the longitudinal axis 9of the machine frame 2 and/or to the position of the loading surface 15of the means of transport 10, provided that a location of the positionof the loading surface 15 is specified.

In addition, an image-capturing device 28 may be specified which createsa real or virtual view from the perspective of the operator or from thebird's eye perspective in the form of an image. The bird's eyeperspective is preferably created above the virtual axis of rotation 19of the trajectory 25. The control system 24 may insert the virtualtrajectory 25 into the image created by the image-capturing device 28and displayed on the image-displaying device 30.

The milling machine 1 a represented schematically in FIG. 6 bycontinuously drawn lines shows the starting position in which acoordinate system X, Y is defined relative to the milling machine. Inthis embodiment, the specified trajectory 25 is on one axis with thelongitudinal axis 9 of the machine frame 2 in the starting position.When the milling machine 1 a begins to move, the distance traveled bythe milling machine and the steering angle adjusted in the process arecontinuously detected via sensors 50 to 52.

The distance traveled by a reference point on the machine frame 2, forexample, the slewing axis 23, and the altered alignment of the machineframe 2 relative to the Y-axis of the coordinate system (angle β) can bedetermined from these data. The position and alignment of the machineframe 2 of the milling machine in the coordinate system X, Y definedduring initialization can thus be determined unambiguously. Inconjunction with the position and alignment of the trajectory 25 whichis also determined unambiguously in the coordinate system, the slewingangle α can thus be determined in such a fashion that the referencepoint, which in FIG. 6 is the end 13 of the transport conveyor 12, islocated on the trajectory 25.

In this context, it may be specified for the control system 24 tocontinuously establish the altered position data in the coordinatesystem X, Y of the milling machine 1 a in relation to the startingposition.

Alternatively, this process may be performed iteratively, that is,following control to adjust the current slewing angle, a new coordinatesystem (X′, Y′) may be defined at a “new” position of the millingmachine (represented in dotted lines) in that the current position isadopted as the starting position. The position of the trajectory is thentranslated relative to said new coordinate system X′, Y′ and stored, andin the case of a further change in the position of the milling machine,the relative movement of the milling machine is established in the newcoordinate system X′, Y′.

In FIG. 6, an example is depicted as to how the slewing angle α can becalculated in the coordinate system Y, X. For this purpose, referencepoints A, B are determined at the machine frame 2 which have thecoordinates A=(x1, y2) and B=(x2, y2) in the coordinate system X, Y. Thereference point A may, for example, be the slewing axis 23. In FIG. 6,the reference point A would have the co-ordinates x1, 0; it isunderstood, however, that the reference point A may also have thecoordinates (0, 0) in relation to the coordinate system X, Y. In theembodiment according to FIG. 6, the trajectory 25 is a straight linewhich may be entered in the coordinate system X, Y via a linearequation.

FIG. 6 shows a starting situation in which the longitudinal axis of themachine frame 2, the longitudinal central axis 17 of the transportconveyor 12 and the trajectory 25 are collinear. When, followinginitialization, the milling machine 1 a has moved to the position of thereference points A′ (x1′, y1′) and B′ (x2′, y2′), the distance a to thetrajectory 25 can be calculated as follows:

In an initial step, the angle β between the longitudinal axis 9 of themachine frame 2 and the trajectory 25 extending parallel to the Y-axisof the coordinate system X, Y needs to be determined, where the lengthbetween the reference points A and B is given with l1, and the length ofthe opposite cathetus b in the right-angled triangle in which the lengthl1 forms the hypotenuse is calculated from the difference of thex-coordinates of the reference points B′ and A′ as follows:b=|x1′−x2′|

For the dotted position of the milling machine, the angle β between thelongitudinal axis 9 and the Y-axis of the coordinate system, andtherefore the trajectory 25 then results in:β=arc sin [(x1′−x2′)/l1]

For the calculation of the slewing angle α to be adjusted, the distancea of the reference point A′ to the trajectory 25 results from:a=|x1′−x1|,

where x1 is also the constant x-coordinate of the trajectory 25.

The angle α to be adjusted results from the sum of the previouslydetermined angle β and the angle γ, where γ is the angle between thelongitudinal central axis 17 of the transport conveyor 12 and thetrajectory 25 resulting from the adjustment of the slewing angle β.

With the given length 12 between the slewing axis 23 and the referencepoint of the transport conveyor 12 projected on the coordinate system,the angle γ can be calculated as:γ=arcsin(a/l2).

In the embodiment according to FIG. 6, the reference point of thetransport conveyor 12 is the discharge end 13 of the transport conveyorwhere the virtual axis 19 may also be specified.

Instead of determining the position of two reference points on themachine frame A, B, it may also be specified to determine the positionof a single point only if the angular change of the longitudinal axis 9of the machine frame relative to the starting position is additionallydetermined based on the distance traveled and the steering anglesadjusted in the process. The angle β can thus be determined directly.

FIG. 7 shows a possible structure of the control system 24 within thecontroller 3 and the elements interacting with the same. In thisarrangement, proceeding from a starting position of the milling machine1 a, 1 b during the initialization for tracking the change in positionof the milling machine 1 a, 1 b, the control system 24 may receivesignals 50 to 55 from the controller 3 or directly from correspondingdetectors.

The controller 3 may specifically transmit to the control system 24signals 50 relating to the steering angle and steering mode, signals 51relating to the travel speed, signals 52 relating to the distancetraveled, signals 53 relating to the current slewing angle, signals 54relating to the conveying speed of the transport conveyor 12, as well assignals 55 relating to the elevation angle of the transport conveyor.

The control system 24 additionally receives signals from theimage-capturing device 28, the control operating element 27, and in turnemits video signals to the image-displaying device 30.

Moreover, the control system 24 may comprise, in all embodiments, amonitoring device 34 which compares the calculated slewing angle α witha specified maximum slewing angle range for the slewing angle and, inthe case of the maximum possible or permissible slewing angle beingexceeded, generates an alarm signal for the operator and/or a stopsignal for the milling machine 1 a, 1 b.

Notwithstanding the above, the monitoring device 34 may also generate analarm signal for the operator or a stop signal for the milling machine 1a, 1 b if the maximum possible or permissible slewing angle range of thetransport conveyor is not sufficient to follow the trajectory.

The control system 24 also emits, via a CPU processor unit 68, theopen-loop control or closed-loop control signal, respectively, for theslewing angle α to activate the piston-cylinder units 18 for adjustingthe slewing angle, where the monitoring device 34 may be interposed.

Moreover, the control system 24 may, besides activating thepiston-cylinder units 18, additionally also perform the activation ofthe piston-cylinder units 20 and/or an alteration of the conveying speedof the transport conveyor 12.

The automatic control of the slewing angle α is effected in such afashion that the reference point of the transport conveyor 12 alwaysremains on the trajectory 25.

In the process, the calculation of the slewing angle α is effected onthe basis of the known dimensions of the machine frame 2 and thetransport conveyor 12, and the data of the coordinate system stored inthe memory 58, and the trajectory 25.

When the initialization process is started, the position of thecoordinate system may be determined in the memory 58, and a trajectory25 to be specified may be selected or altered and stored in thecoordinate system. During initialization, the coordinate system isaligned preferably parallel to the longitudinal axis 9 of the machineframe 2, and the origin of the coordinate system is placed, for example,on the slewing axis 23. There is also always the possibility tore-determine the origin and alignment of the coordinate system X, Yrelative to the machine frame 2 and to thus reinitialize the coordinatesystem as shown, for example, in FIG. 6 with the coordinate system X′,Y′. During initialization, the longitudinal axis 9 of the machine frame2, as well as the longitudinal central axis 17 of the transport conveyor12, as well as the loading surface 15 of the means of transport 10, arepreferably aligned collinearly.

Different trajectories 25 can be selected and positioned in thecoordinate system via the operating element 27. In the simplest case,the trajectory is a straight line. The position of the trajectory 25 inthe coordinate system can be altered by means of the operating element27; as shown in FIG. 4, the trajectory 25 can, for example, be slewedabout the virtual vertical slewing axis 19.

The information on the trajectory 25 entered, for example, via thecontrol element 27 or via an input device of the controller 3, as wellas, where appropriate, the video signals of the image-capturing system28 may be emitted to the image-displaying device 30 in a combinedfashion so that the operator can monitor the automatic operation of theslewing angle control starting after the initialization of the millingmachine 1 a, 1 b on the image-displaying device 30 and, should the needarise, can influence the orientation of the trajectory 25 by means ofthe control operating element 27.

Moreover, the control system 24 may receive signals from adistance-measuring device 40 by means of which the distance to a meansof transport 10 following behind or driving ahead is detectable.

The control system 24 may continuously detect the position of theloading surface 15 and/or the transport conveyor 12 by means of theimage-capturing system 28 or a non-optical electronic location system 62which supplies data for determining the position of the loading surface15 and for display on the image-displaying device 30 in relation to themachine frame 2 or to the transport conveyor 12. The information fromthe image-capturing system 28 may be evaluated by means ofimage-analysing methods which are known for themselves. An example of anon-optical electronic location system is a radio-frequencyidentification system (RFID) which additionally offers the possibilityto identify a specific loading surface 15 of a specific means oftransport 10.

When locating the loading surface 15 by means of RFID, stationary RFIDtags may be used at the means of transport 10, specifically, at theloading surface 15.

Alternatively or additionally, signals from a GNSS device 56, forexample, GPS, GLONASS, Galileo, may be entered for positiondetermination. The machine frame 2 preferably possesses, as a minimum,two GNSS receivers 64, 66 attached in different positions on the machinewhich, in addition to the position, also determine the alignment of themachine frame 2.

The trajectory 25 is determined in the memory 58 relative to thecoordinate system by means of, for example, the operating device 27.During initialization, the trajectory 25 may, for example, initially bedetermined relative to the machine frame 2. The coordinates of thetrajectory 25 in the GNSS coordinate system can therefore be establishedand transferred into the memory 58 based on the position of thetrajectory 25 in relation to the coordinates of the machine frame 2 orthe slewing axis 23.

As soon as the milling machine 1 a, 1 b changes its position, thealtered GNSS position coordinates of the machine and the machinealignment are detected while the coordinates of the trajectory withinthe GNSS coordinate system re-main unchanged. The relative movementbetween the machine frame 2 and the trajectory 25, as well as theangular change between the trajectory 25 and the longitudinal axis 9 ofthe machine frame 2 can thus be established and, as a result, theslewing angle α controlled in such a fashion that the reference point ofthe transport conveyor 12 is on the coordinates of the trajectory 25.

In case of a change in the course of the trajectory 25, it is necessaryto change the coordinates describing the trajectory 25.

Determination of the machine position and of the alignment of the sameis known prior art.

Two GPS sensors 64, 66 are shown in FIG. 4, for example, by means ofwhich it is possible to determine the position and to determine thealignment of the machine frame 3.

What is claimed is:
 1. A self-propelled milling machine for milling aground surface, comprising: a machine frame with a longitudinal axis; aheight-adjustable working drum; a slewable transport conveyor arrangedin front of or behind the working drum as seen in the direction oftravel of the milling machine, with a discharge end from whichworked-off milling material is dischargeable onto a point of impingementon a loading surface of a transport vehicle, wherein the transportconveyor is laterally slewable to a slewing angle, about at least afirst slewing axis extending essentially orthogonal to the machineframe; and a controller configured to control the slewing angle of thetransport conveyor automatically in travelling and milling operations,at least as a function of a virtual trajectory for positioning thetransport conveyor which is specified in a stationary coordinate systemindependent of the position and alignment of the machine frame, whereina reference point of the transport conveyor remains on the specifiedtrajectory responsive to a change in position of the machine framewithin the coordinate system.
 2. The self-propelled milling machine ofclaim 1, wherein the reference point of the transport conveyor comprisesthe discharge end of the transport conveyor or the point of impingementof the worked-off milling material.
 3. The self-propelled millingmachine of claim 1, wherein the self-propelled milling machine is a roadmilling machine.
 4. The self-propelled milling machine of claim 1,wherein the self-propelled milling machine is a surface miner.
 5. Theself-propelled milling machine of claim 1, wherein the self-propelledmilling machine is a recycler.
 6. The self-propelled milling machine ofclaim 1, wherein the controller is configured to continuously detect thecurrent position and alignment of the machine frame in the coordinatesystem and to determine the slewing angle to be adjusted as a functionof the position of the specified trajectory relative to the machineframe.
 7. The self-propelled milling machine of claim 1, wherein thecontroller is configured to continuously detect the current position andalignment of the machine frame in the coordinate system and to determinethe slewing angle to be adjusted as a function of the position of thespecified trajectory relative to the reference point of the transportconveyor.
 8. The self-propelled milling machine of claim 1, wherein thecontroller is configured to alter a position of the trajectory relativeto the stationary coordinate system, and to recalculate a currentslewing angle in response thereto.
 9. The self-propelled milling machineof claim 1, wherein the controller is configured, responsive to inputfrom an operator and a desired change in the position of the trajectory,to determine a different course of the trajectory in the coordinatesystem.
 10. The self-propelled milling machine of claim 1, wherein thecontroller is configured, responsive to input from an operator, to slewthe alignment of the trajectory in the coordinate system about a presetvirtual axis of rotation extending essentially orthogonal to the groundsurface.
 11. The self-propelled milling machine of claim 1, furthercomprising an image-displaying device which graphically represents atleast a relative position of the trajectory in relation to the transportconveyor.
 12. The self-propelled milling machine of claim 1, furthercomprising an image-displaying device which graphically represents atleast a relative position of the trajectory in relation to thelongitudinal axis of the machine frame.
 13. The self-propelled millingmachine of claim 1, further comprising an image-displaying device whichgraphically represents at least a relative position of the trajectory inrelation to the position of the loading surface of the transportvehicle.
 14. The self-propelled milling machine of claim 1, furthercomprising an image-displaying device which graphically represents atleast a relative position of the trajectory in relation to the transportconveyor and to the longitudinal axis of the machine frame.
 15. Theself-propelled milling machine of claim 1, further comprising animage-displaying device which graphically represents at least a relativeposition of the trajectory in relation to each of the transportconveyor, the longitudinal axis of the machine frame, and the positionof the loading surface of the transport vehicle.
 16. The self-propelledmilling machine of claim 1, wherein the controller is configured tocontinuously detect the steering angle and the distance travelled, andto calculate the current position and alignment of the machine frame inthe coordinate system based at least in part thereon.
 17. Theself-propelled milling machine of claim 1, wherein the controller isconfigured to continuously detect the steering angle and the currenttravel speed, and to calculate the current position and alignment of themachine frame in the coordinate system based at least in part thereon.18. The self-propelled milling machine of claim 1, wherein thecontroller is configured to continuously detect the position andalignment of the machine frame relative to the coordinate system via aGNSS position determination device, and to calculate the currentposition and alignment of the machine frame in the coordinate systembased at least in part thereon.
 19. The self-propelled milling machineof claim 1, wherein the controller is configured to determine thedistance (a) between a reference point and the trajectory, and the angleB between the longitudinal axis of the machine frame and the trajectory.20. The self-propelled milling machine of claim 19, wherein thereference point is on the longitudinal axis of the machine frame. 21.The self-propelled milling machine of claim 1, wherein the transportconveyor is pivotable to a specified elevation angle and about a secondaxis extending orthogonal to the first slewing axis, wherein thetransport conveyor discharges the milling material onto the loadingsurface of the transport vehicle at a specified conveying speed, andwherein the controller is configured to continuously control the slewingangle of the slewable transport conveyor automatically as a function ofat least one of the following parameters, namely, the longitudinal andtransverse inclination of the machine frame, the advance speed, theelevation angle of the transport conveyor and the conveying speed of themilling material, in such a fashion that, in any steering situationduring forward travel or reverse travel, the slewable transport conveyorassumes a specified slewing angle in which the reference point of thetransport conveyor is guided along the trajectory.
 22. Theself-propelled milling machine of claim 1, wherein the transportconveyor is inclinable to a specified elevation angle and about a secondaxis extending orthogonal to the first slewing axis, wherein thetransport conveyor discharges the milling material onto the loadingsurface of the transport vehicle at a specified conveying speed, and thecontroller is further configured to control either or both of theelevation angle of the transport conveyor and the conveying speed of thetransport conveyor automatically, in such a fashion that the referencepoint of the transport conveyor always remains on the specifiedtrajectory in the case of a change in position of the machine framewithin the coordinate system.
 23. The self-propelled milling machine ofclaim 1, wherein the controller is configured to continuously locate theposition of the loading surface in the coordinate system, and to controlthe slewing angle to maintain the discharge end of the transportconveyor or the point of impingement along the specified trajectorywithin the loading surface.
 24. The self-propelled milling machine ofclaim 1, further comprising an image-capturing device which creates animage view from a perspective of the operator or from a bird's eyeperspective, wherein the controller is configured to insert a virtualtrajectory into the image created by the image-capturing device anddisplayed on an image-displaying device.
 25. The self-propelled millingmachine of claim 24, wherein the created image view is a real or virtualview created above a virtual axis of rotation of the trajectory.
 26. Amethod for controlling a self-propelled milling machine for milling aground surface, wherein milling material worked off by a working drum inthe milling operation is transported away by a transport conveyorcomprising a discharge end, and is discharged from the discharge endonto a point of impingement on a loading surface of a transport vehicle,and wherein the transport conveyor can be automatically slewed at leastlaterally in the travelling and milling operation, the methodcomprising: receiving one or more inputs to a controller specifying avirtual trajectory for positioning the transport conveyor or the pointof impingement which is freely selectable in a stationary coordinatesystem that is independent of the position and alignment of the machineframe; and controlling at least the slewing angle of the transportconveyor in such a fashion that a reference point of the transportconveyor is always kept on the specified trajectory responsive to achange in position of the milling machine in the coordinate system. 27.The method of claim 26, comprising: continuously detecting a currentposition and alignment of the machine frame in the coordinate system,and determining the slewing angle to be adjusted as a function of theposition of the specified trajectory relative to the machine frame. 28.The method of claim 26, wherein a different trajectory is entered in thecoordinate system, responsive to a desired change in the course of thetrajectory.
 29. The method of claim 26, comprising: altering analignment of the trajectory in the coordinate system about a presetvirtual axis of rotation extending orthogonal to the ground surface,responsive to a desired change in the course of the trajectory.
 30. Themethod of claim 26, comprising: altering an alignment of the trajectoryin the coordinate system about a preset virtual axis of rotationextending orthogonal to the ground surface and located on or in anextended axis of the transport conveyor, responsive to a desired changein the course of the trajectory.
 31. The method of claim 26, wherein acurrent position and alignment of the machine frame in the coordinatesystem are calculated by continuously detecting parameters selected froma group comprising one or more of: a steering angle and distancetravelled; the steering angle and a current travel speed; and a positionand alignment of the machine frame relative to the coordinate system, asdetected via a GNSS position determination device.